By-pass valve for hydraulic motors



July 21, 1953 ci E. DEARDORFF 2,646,025

BYPAss VALVE FOR HYDRAULIC MOTORS Flved Feb. 7, 1951 ATTORNEY Patented July 21, 1953 UNITED stares CFFICE I 2,646,025 BY-EYASS VALVE FOR HYDRAULIC MOTORS Clinton E. Deardorff, San Fernando, Calif., as-

signor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application February 7, 1951, Serial No. 209,848

tion is to provide a satisfactory valve for bypassing fluid from the outlet to the inlet of the motor when the latter outruns its fluid supply, without interfering withl the normal operation of the motor in the other direction.

Other more specific objects and features of the invention will become apparent from the descriprtion to follow with reference to the drawing.

' In the drawing:

Fig. l is a schematic diagram of a hydraulic landing gear system incorporating a valve in accordance with the present invention, the valve being shown in longitudinal section.

Fig. 2 is a view similar to Fig. 1 but showing lthe apparatus in a different phase of its operation.

In Fig. 1 there is indicated schematically a hydraulic landing gear for an airplane, the gear consisting of an arm Iii adapted to be swung i about a pivot II from an elevated or retracted position, as indicated at Ilia, into a fully lowered position Illb. A rubber tired wheel I2 is indicated on the outer end of the arm I 0. To actuate the arm I through its range of movement, it is connected bya rod I3 to the piston I4 of a hydraulic motor cylinder I5; the latter being pivotally supported as by a pivot I3 to the frame' of the airplane. The upper end of the cylinder I5 is connected directly by a duct I'l to one of the output ports of a Ll-way selector valve I8. The lower end of the cylinder I5 is connected by a duct v23 to one port 29 of a valve I9 in accordance with Ithe present invention, and another'port 26 yof this valve is connected by a duct to the other 'output port of the Ll-way 'selector valve I8. The

selector Valve IB is provided with a pressure supply'line 2l, and an exhaust line 22.

If the valve I9 were not interposed in the system, the duct 2s would be connected directly to the duct 20, which, when the valve I8 is in the position shown in Fig. l, is connected to exhaust whereas the other duct Il is connected to the pressure fluid supply. rlhis pressure fluid supply originates at a pump which usually has a limited volumetric capacity. During downward movement of the arm I0, the weight of the arm I0 `and the wheel I2 is often sufcient to carry the piston I4 downwardly in the cylinder I5 faster than fluid can be supplied thereto through the duct I'I from a pump. rllhe result is that the piston I4 draws a vacuum in the upper end of the cylinder I5 until the arm I0 `isy near its lower 2 position, whereupon the mechanism waits until the pump has filled the cavity in the upper end of the cylinder I5, before pressure is developed therein to complete the movement of the arm I0 into its lowermost position, as illustrated at Inb.

The purpose of the valve I9 is to permit iluid from the lower end of the cylinder I5 to be bypassed throughthe duct'23, the valve I9, and the duct I I back to the upper end of thecylinder I5 when the movement of the piston I 4 in re- Asponse to the weight of the landing gear develops a higher pressure in the duct 23 than in the duct I 'I'. This bypass of fluid maintains the upper end of the cylinder l5 lled with fluid at all times. Therefore, as soon as the downwardrmovement of the piston I4, by gravity, is terminated, the pressure iiuid supplied by the pump can move the piston into its full lowermost position. However, the valve I!! mustr prevent the bypass of iluid from the duc-t 23 to the duct' Il', when the 7 landing gear is being raised by admission of pressure iluid through the duct 2|] and exhaust of fluid through the duct I'I. A

Thebody of thevalve I9 defines a cylinder 24 containing a piston 25 reciprocable therein.y The left end of the cylinder 24 is in communication With the port 25 which is connected to the duct 20, and' the right end of the cylinder is connected. by 'a passage Zlfwith the port 28 that is connected to the duct I'I. The port 2S to which the duct'23 is connected is also in communication with the right end of Athe cylinder 24.

Thepiston25 is hollow, having'` a passage 30 extending therethrough, which' passage terminates at the left endof' the piston in a valve seat 3i adapted to be engaged by a poppet vvalve 32. This poppet Valve 32 `is connected by a stem` 33 with a second poppet valve 334 which is adapted to close against a 'seat 35 at the inner end of the passage 2l. A head 3l' on the stem 33 slideably engages the right end of the'piston 25 to guide the Vpo'ppets relative to the piston. The outer end of the passage 21 is normally closed by a ball check valve 38 which. permits iiow into the port-28 but not outwardly therethrough. The piston 25 is urged to the left by a helical compression spring 40, and the poppet 32 is urged to the right by a helical compression spring 4I.

The spring 4I is of suiiicient length to close the poppet 34 against the seat 35 as shown in Fig. 2,- The length of the'stern 33 is suchthat with the piston 25 in its left limitv position and the poppet 32 seated on seat 3 I, the seated from the seat `35.

It will be observed that the springs 4I and 40 poppet 34 is unare in opposing relation and that the position of the assembly consisting of the poppet 32, poppet 34 and piston 25 will be dependent upon the relative forces of these two springs, in the absence of pressure forces. The springs may be balanced so that the left end of piston 25 is away from a stop 45 constituted by the inner end of a closure plug 45 containing the port 25, and the poppet 34 is away from the seat 35. If the spring 40 is stronger, the piston 25 will normally rest against the stop 45, whereas if the spring 4| is stronger the poppet 34 .will normally rest against the seat 35. The strength of the springs relative to each other is not of major importance, but they should both be light so that the position of the assembly is responsive to relatively slight pressure diierentials. Thus a relatively small reversal in the diierential pressure between ports 26 and 29 should shift the valve between the two positions shown in Figs. 1 and 2 respectively. In practice it may be desirable to make spring 40 slightly stronger than spring 4I so that poppet 34 is open in the absence of pressure forces.

The head 3'! has mounted in an annular groove thereon a snap ring 41 which is engageable with theright end of the piston 25 to limit leitward movement of the head 33 `relative to the piston ,25, as shown in Fig. 2.

The system functions as follows. first Fig. l, in which the selector valve I8 is adjusted to connect the duct Il to the pressure supply line 2|, and the duct 20 to the exhaust line 22. At this time, the weight of the landing gear is urging the piston I4 downwardly and tends to move the piston faster than fluid `is supplied to the upper end of the cylinder by the pump through the selector valve I8. This produces a pressure in the duct 23 that is higherthan that in the duct Il, With the result that -the iiuid ows from the lower end of the cylinder I5 through the duct 23 into the port 29 of the valve I9, and thence through the passage 21 past the check valve 38 and through the port 28 to the duct I'I, where it mixes with the fluid being supplied by the pump through the pressure line 2|, and ows on into the upper end of the cylinder I5. Poppet 34 is unseated at this time because the pressure in port 29 is higher than that in port 26, creating a pressure differential across piston 25 holding the latter against the stop 45.

Since some fluid is being supplied'through the pressure supply line 2 I, the total amount of fluid flowing through the duct into the upper end of the cylinder l5 will increase the pressure in the duct 23 above that in the duct 23. When vthis pressure develops a force against the poppet 34 suicient to overcome the force of the spring 4|, the assembly consisting of the poppets 34 and 32 is moved to the left permitting the excess fluid entering the port 29 to flow through ports 43 in the piston 25, into the center space in the piston and thence past the poppet 32 and out through the port 26 to the duct 20. The overall result is that suicient fluid is bypassed through the valve from port 29 to port 28 to make up the deficiency in the upper end of the cylinder I5 resulting from the fact that the piston I4 is creating space in the upper end of the cylinder faster than the pump can supply it, and the excess fluid equal to that being supplied by the pump through the pressure line 2| is permitted to escape past the poppet 32 into the duct 2|] and thence back to the exhaust line 22.

The landing gear shown in Fig. 1, and as Consider usually constructed, is of such nature that it is incapable of moving into its full lowermost position by gravity. At some point near the lower limit of movement of the piston I4, the mechanism has to be moved by pressure uid in the upper end of the cylinder I5. Hence when the piston I4 begins to oier resistance to the downward movement, the pressure rises in the upper end of the cylinder I5 and inthe duct I'I. This increase in pressure prevents opening of the check valve 38, so that thereafter all of the fluid exhausted through the duct 23 escapes past the poppet 32 into the duct 23 and thence back to the exhaust line 22.

Referring now to Fig. 2, when the landing gear is to be retracted, Jthe selector valve I8 is rotated through a quarter turn to connect the pressure supply line 2| to the duct 20, and connect the exhaust line 22 to the duct The pressure iluid in duct 20 enters the port 23 and is applied against the left end of the piston 25 and the poppet 32, tending to move them as a unit to the right. The piston and the poppet do move as a unit to the right until the poppet 34 seats against the seat 35. Thereafter the piston 25 moves alone carrying the seat 3| away from the poppet 32. This opens a passage for the flow of pressure iiuid from the duct 2|] through the port 23, past the valve seat 3| into the hollow piston, and thence through the passages 43 to the port 23 and through the duct 23 connected thereto, to the lower end of the cylinder I5. As the piston I4 is moved upwardly by the flow of pressure fluid into the cylinder therebelow, fluid in the upper end of the cylinder is exhausted through the `duct Il and the valve I3 to the exhaust line 22. At this time the passage 2 connecting the cylinder 24 with the port 28 is blocked against flow of liquid in either direction, the poppet 34 blocking flow out of the cylinder 24, and the check valve 3B blocking ow into the cylinder.

It will be observed, therefore, that the valve functions to bypass uid from the port 23 to the port 28 when the pressure in port 29 exceeds that in port 23, and there is no pressure existent in the port 23. On the other hand, when pressure iiuid is present in the port 25, the bypass action oi the valve is disabled, and there can be no transfer of pressure fluid either from the port 25 or the port 29 to the port 28.

The seat 3| on the piston 25 remains unseated from the poppet 32 only while there is ow of iiuid into the port 25 and past the seat 3| to produce a pressure drop across the seat. Whenow ceases, the pressure forces on the piston 25 are -balanced and the piston is moved to the left back into engagement with the poppet 32 by the spring 43. However, as long as the pressure in the port 23 is higher than that in the port 28, the pressure forces on the assembly comprising the poppet 32, the stem 33 and the poppet 34 will be unbalanced and the assembly will be retained in its rightmost position as shown in Fig. 2, with the poppet 34 sealing against the seat 35.

Although for the purpose of explaining the invention a particular embodiment thereof has been shown and described, obvious modifications will occur to a person skilled in the art, and I do not desire to be limited to the exact details shown and described.

I claim:

1. A valve for use with a reversible hydraulic motor having a pair of ducts and means for si- U multaneously connecting either duct to a source of pressure iiuid and the other duct to exhaust. said valve comprising: a valve body having first land second ports adapted to be connected in series in one of said ducts with said second port nearest the motor, land a third port adapted to be connected to the other 'of said ducts; said body dening a passage interconnecting said rst and second ports; rst valve means in said passage comprising a pair of Ycooperating valve elements both movable in said passage and movable relative to each other between open and closed positions; rst spring means urging one element away from said first port and in valve closing direction with respect to the other element; second spring means Vurging the other valve element toward said first port and in valve closing direction with respect to said one element; said valve elements having pressure faces responsive to differential pressures between said rst land second ports to open said rst valve means in response to a pressure diierential of v predetermined magnitude between said first and second ports in either direction; second normally closed valve means between said second and third ports, and means responsive to pres- `sure in said second port exceeding the pressures in both said said rst and third ports for opening said second valve means.

2. A valve according to `claim 1 in which one of said valve elements-comprises a piston member in said passage, said piston member having a passage therethrough, and the other of said valve` elements comprises a closure member movable into and out of closing relation with said passage in said piston member.

3. A valve according to claim 1 in which said second valve means `comprises a valve seat in communication with said third port, a poppet therefor, and means connecting said poppet to said rst valve means for opening said poppet 01T said seat in response to movement of said rst valve means toward said first port.

4. A valve according to claim 3 in which said second valve means includes a check valve between said valve seat and said third port for permitting flo-w through said third port into said valve and preventing reverse iiow.

5. In combination, a reversible hydraulic motor having a pair of ducts; a selector valve having a pair of motor ports; `a bypass valve comprising a valve body having rst and second ports connected in series between one motor duct and one motor port of said selector valve with said second port nearest the motor, said valve body having a third port connected to the other motor duct and the other motor port of said selector valve in parallel; said valve body dening a passage interconnecting said first and second ports; the first valve means in said passage comprising a pair of cooperating valve elements both movable in said passage and movable `relative to each other between open and closed positions; first spring means urging one element away from said rst port and in valve closing direction with respect to the other element; second spring means urging the other valve element toward said iirst port and in valve closing direction with respect to said one element; said valve elements having pressure faces responsive to differential pressures between said first and second ports `to open said first valve means in response to a pressure differential of predetermined magnitude between said rst and second ports in either direction; second normally closed valve means between said second and third ports, and means responsive to pressure in said second port exceeding the pressures in both said first and third ports for opening said second valve means.

6. A valve for use with a reversible hydraulic motor having a pair of ducts and means for simultaneously connecting either duct to a source of pressureu'iuid and the other duct to exhaust, said valve comprising: a valve body having rst and second ports adapted to be connected in series in one of said ducts with said second port nearest the motor, and a third port adapted to be connected to the otherof said ducts; said body defining a passage interconnecting said rst and second ports; first valve means in said passage comprising a first movable valve seat reciprocable in said body and interconnecting said irst and second ports; a first poppet for said iirst seat on the rst port side thereof independently reciprocable in said body toward and away from said first seat; spring means urging said rst seat and said rst poppet toward seating relation with each other; a second stationary valve seat interconnecting said second and third ports, and a second poppet for said stationary seat on the second port side thereof; a stop limiting movement of said rst seat toward said lirst port; means interconnecting said first and second poppets for movement in unison and in such spaced relation that movement of said first seat against said stop unseats said second poppet; whereby pressure in the first port exceeding pressure in the second port seats said second poppet and unseats the first seat from the first poppet, and pressure in the second port exceeding the pressure in the rst port unseats both poppets; and a check valve for preventing flow from said third port to said second seat.

7. A valve according to claim 6 in which said spring means comprises two separate springs one between said body and said poppets and urging them toward their seats and the other between said body and said movable seat and urging it toward said rst seat and said stop.

8. A valve according to claim 7 in which said other spring is stronger than said one spring whereby it unseats said second poppet in the absence of pressure forces aiding the one spring.

CLINTON E. DEARDORFF.

References Cited in the le of this patent UNITED STATES PATENTS Number 

